Baseline evaluation for natural radioactivity level and radiological hazardous parameters associated with processing of high grade monazite

摘要

Egyptian monazite is a promising resource and investment attractive for production of valuable metals of industrial or nuclear interest such as rare earth elements (REEs), thorium (Th) and uranium (U). The study was focused to establish a baseline framework in viewpoint of radiation protection for the workers in production of REEs from high-grade monazite treated by sodium hydroxide (NaOH) solutions. Radiological hazard indices (cancer, gonadal and other risks) were evaluated, due to emissions (alpha-, beta-and gamma-radiations) of radium-isotopes (Ra-228, Ra-226, Ra-223) and lead (Pb-210). The values of the estimated radiological hazard indices were higher than the permissible safe limits, worldwide average and varied with those reported in other countries. It was found that more than 70% of radioactivity and radiological hazardous indices resulted from emissions of Ra-228, while the rest was attributed to 226Ra, 223Ra and Pb-210. Therefore, processing of the Egyptian monazite can cause a significant radiological impact on workers through external exposure from gamma-radiations and/or internal exposure through inhalation or ingestion airborne contaminated by the radionuclides. Thus, the results recommended that protection rules could be considered to prevent the radiation hazards associated with the production of the REEs from the high grade monazite attacked by caustic method. (C) 2017 Elsevier Inc. All rights reserved.